STM32WB55 OpenThread Low Power Issue

[hdw]

We are encountering an issue with the STM32WB55CGU when using it in combination with OpenThread, particularly related to the low power mode. Below are the details of the issue:

1. Software Versions:

   • STM32CubeIDE version: 1.16.0
   • STM32WB55 firmware version: 1.20
   • OpenThread version: Configurations are attached in the .ioc file.

2. Problem Description: We have configured the STM32WB55 to enable low-power mode, but we are experiencing the following issues:

   • The first time after enabling low-power settings, the software runs, but the MCU does not enter low-power mode as expected.
   • After cycling the power (removing and reapplying it), the MCU crashes almost immediately upon startup.

3. Configuration: The low power mode was configured using the standard function available in the STM32CubeMX .ioc file. No external peripherals are involved in this setup.

4. Observations:

   • When low power mode is disabled, the OpenThread stack runs as expected. We observe that the access point receives a poll every 5 seconds.
   • The issue does not occur when using a debugger. The code works as intended while debugging.
   • We tested the same software on an ST development board, and it performed correctly in the same conditions, leading us to believe this could be a configuration issue rather than a hardware fault.

5. Additional Question: We also noticed that it is necessary to select a UART for OpenThread, even though it is not being used in our configuration. If the UART is not selected, we encounter an error when generating the code. Could you please clarify why this is required and if there is a way to avoid this dependency?

6. Attempts to Resolve: We have tried monitoring the behavior using the debugger, but the issue does not reproduce in debug mode. Unfortunately, we do not have any logs or specific error messages available when the issue occurs.

Attached is the .ioc file for reference. We would appreciate your assistance in identifying any potential configuration issues or providing guidance on how to debug this problem further in low power mode.

[STTwo-32]

Hello @hdw 

On the Wireless applications, we are using the LPM (Low Power Manager) to control the Low power modes on the sequencer that is used to control the execution of the different tasks. More details available on this AN5289.

Best Regards.

STTwo-32